Back on navies problems, as I did restarted to play that game.
playing the french, against the AI, I noticed the optimum amount of ships is 12 ships (10 + 2 frigates), with a back up of 6 ships that are restaured.
The best positioning being Brest up to june 1805, and then move to Calais(?) for a crossing.
I usually finish the english navy by that time, having captured over 20 ships; and that without counting the russians , the portugese, or even the spaniards previously captured by the red coats.
On the other hand, moving from that place earlier is a recipe for catastrophe (early encouter with Nelson for exemple), not having the initial 6 ships as back up ready to be used is a waste of time, and another recipe for catastrophe, because England will start to produce frigates as it was not tomorrow.
Similar to the plan deviced IRL by Latouche Treville, you must cross the channel BEFORE 1st august, and as his plan, it mean an early concentration out of the crossing point (Antilla IRL, here it is Brest), taking the english fleet piece meal (even Nelson with 8 ships can not compete if you hammer him every 2 days with 12 ships, and disengage after 24 hours).
As IRL, even Nelson can be beatten badly (he did, 3 times, against the same person, Latouche Treville, who used hit and run tactic, near Brest!), as long as you are a bit gamey (disengage after 24 hours most of the time, using the fact the AI will not move for the next 24 hours, then you come back with ready to fight ships while the AI still have hurted ships).
Perso, I find it very close to the naval condition of the time, where little can be done against an ennemy strongly positioned into a good port; while at the opposite that one can hit and run your blockade quite well and destroy you slowly.